Research
Hormonal
Evening exposure to artificial light, particularly from LED screens and smartphones, delays circadian phase, suppresses melatonin, and reduces sleep quality and duration.
Avoid bright screens (phones, tablets, LEDs) for at least 2-4 hours before bedtime. If you must use them, dim the brightness to the lowest possible level and use 'night mode' to reduce blue light. Be aware that psychological engagement from content may also disrupt sleep, so consider winding down with non-screen activities.
GoodSupportsHIGH confidence
Indeed, light from LED screens has repeatedly been suggested to interfere with sleep and the physiological processes involved (e.g., melatonin secretion [24]). Chang and colleagues [26] for example found that reading a book from an e-reader for four hours before sleep increased sleep onset latency, reduced evening sleepiness, melatonin secretion as well as next-morning alertness, and delayed the timing of the biological clock...
Why this rating
Multiple studies cited show consistent effects, though the paper notes confounding variables.
Source
Effects of light on human circadian rhythms, sleep and mood
Christine Blume et al. · Somnologie - Schlafforschung und Schlafmedizin · 2019
DOI 10.1007/s11818-019-00215-x
narrative_reviewCited 640×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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